I. Field of the Invention
The invention is directed to a railborne mobile crane with an auxiliary car which is coupled to the crane car and has a supporting device for the head of the boom during transport, wherein the boom lies essentially horizontally and is articulated at the boom base at the pivoting frame of the mobile crane.
II. Description of Related Art
Railborne mobile cranes with transport cars for depositing the boom are generally known. For example, DE-AS 1282271 describes a crane in which, in order to reduce loading of the truck axles, the head of the boom is deposited on a transport car coupled with the mobile crane, so that part of the weight of the boom is received by the transport car.
Another solution for depositing the boom of a mobile crane is described and illustrated in DE-AS 1234959. In this case, reference, in the transport position in which the boom is arranged essentially horizontally, the head of the boom is deposited on a supporting device which is fastened in turn to the transport car, which is called the protection car in the above reference. This reference also addresses the problem that the boom of the mobile crane must be set down so as to be movable because the boom may assume a diagonal position in relation to the auxiliary car when traveling along curves.
While DE-AS 1282271 emphasizes compensation for loading of the axles and suggests that the boom be supported on the chassis of the mobile crane, DE-AS 1234959 described above comes closest to the present invention and forms the prior art on which the present invention improves.
However, the prior art does not take into account the fact that, in addition to the pivoting movements between the mobile crane and the auxiliary car when traveling along curves, still other influences act on the boom which must be taken into account when depositing the boom on a supporting device of the type described. For example, changes in distance between the vehicles occur when they are braked and the bumpers or buffers of the vehicles deflect in a springing manner. The same changes in distance occur as a result of play in the coupling between the mobile crane and auxiliary car or when driving over ramps or acclivities, wherein the mobile crane and the auxiliary car are inclined relative to one another. Superelevation on curves along the stretch of rail must also be compensated for.
In a solution such as that suggested in DE-AS 1234959, all of these influences would have to be absorbed by the supporting device or by the pivot bearing of the release at the pivot frame of the mobile crane. Means and steps for preventing or compensating for this are not provided. This known construction only takes into consideration movements from curve travel into a horizontal plane in that the push rods for the movement of the swivelable roof of the crane protected therein are designed so as to be longitudinally displaceable. However, this is not sufficient for the movements and changes in movement which actually occur.